1. Field of the Invention
The invention relates to a vehicle bumper structure, and in particular to a bumper structure having a bumper absorber that absorbs an impact upon collision with an object.
2. Description of the Related Art
A bumper absorber (impact absorption member) for absorbing an impact upon collision is provided on the vehicle-longitudinal-direction outer side of each of the bumper reinforcements of the front and rear bumpers of a vehicle. The crash safety tests conducted by the Insurance Institute for Highway Safety (IIHS) in the United States include a narrow vertical overlap barrier test. In this test, an arc-shaped barrier is used, the center portion of which is convexed toward the outer side along the vehicle longitudinal direction. The barrier is vertically offset to partially overlap the bumper of the vehicle, and the front and rear sides of the vehicle are made to collide with the barrier at 10 km/h.
In the case of a vehicle that is relatively small in height, the vertical level of each bumper is low as compared to the vertical level of the barrier, and therefore the vertical overlap amount is not sufficient. In this case, because the vertical overlap amount is not sufficient, the vehicle may get into the lower side of the barrier, that is, so-called underride may occur, which can reduce the impact absorption capacity of the vehicle. On the other hand, in the case of a vehicle that is relatively large in height, the vertical level of each bumper is high as compared to the vertical level of the barrier, and therefore the vertical overlap amount is not sufficient. When the vertical overlap amount is not sufficient, the vehicle may run onto the barrier, that is, so-called override may occur, which can reduce the impact absorption capacity of the vehicle. For example, Japanese Patent Application Publications No. 2007-261525 and No. 2007-196827 (JP-A-2007-261525 and JP-A-2007-196827) each describe a bumper structure for preventing underride and override of a vehicle.
However, the technology described in JP-A-2007-261525 is not effective unless the bumper structures of the vehicles that collide with each other are identical. Further, the technology described in JP-A-2007-196827 requires the use of separate members for the bumper reinforcement (bumper beam) in order to increase the vertical overlap amount, and thus it has drawbacks of an increased number of parts, increased assembly time, and increased cost.